Lamb, 30, is charged with residential burglary, possession of stolen firearms and being an "armed habitual criminal."

The state had offered to drop the burglary and armed habitual criminal charges if Lamb pleaded guilty to aggravated possession of a stolen firearm and provided information on others who are suspected in the alleged theft, Combs said.

Lamb was accused of stealing the safe from a friend. Authorities said it had 11 to 20 firearms inside, as well as several rounds of ammunition. Neither the safe nor its contents has ever been recovered.

Combs said the information Lamb could have provided would have aided authorities in getting "those guns off the streets."

The sentencing range on the plea deal was six to 40 years in prison with day-for-day credit, Combs explained.

Prather would have decided on the sentence, but Combs said that accepting the deal could have shaved 5 and a half years off the prison term. Lamb is now being held in McHenry County Jail on a $1 million bond.

Lamb was the state's main witness against his former co-worker, Mario Casciaro, who was arrested in 2010 in the 2002 disappearance of 17-year-old Brian Carrick.

Though Carrick's body has never been found, Casciaro was convicted of murder in Carrick's death after two trials and sentenced to 26 years in prison.

But it was Lamb who admitted from the witness stand during Casciaro's trials that he delivered what might have been a fatal punch to Carrick the night he disappeared.

Lamb said Casciaro had him confront Carrick about a pot-dealing debt he owned Casciaro. Lamb said he punched Carrick, who fell to the ground bleeding and unconscious, in a walk-in cooler at the Johnsburg grocery store where all three worked.

Lamb was never convicted of any crime in connection to Carrick's disappearance, but he has a lengthy criminal record, including a felony battery conviction and misdemeanor convictions for battery, drug possession and resisting arrest.

A burst of thunderstorm activity across the Chicago area in Sunday afternoon resulted in multiple injuries and a death at an event in west suburban Wood Dale, the collapse of a dome in northwest suburban Rosemont and the temporary evacuation of the music festival Lollapalooza in Grant Park downtown.

The father of a 20-year-old Carol Stream, Ill., woman who drowned at Indiana's Porter Beach on Friday night identified her body Sunday afternoon after a rescue team pulled her from Lake Michigan, authorities said.